130 Mr HAIDINGER'S Mineralogical Account of 



Lustre, imperfect metallic. Colour, bluish-black and greyish 

 black, passing into dark steel-grey. Streak, brownish-black, shin- 

 ing. Opaque. 



Brittle. Hardness 5.0 . . . 6.0, between apatite and felspar. 

 Sp. gr. 4.145, a botryoidal variety. 



Compound Varieties. Reniform, botryoidal, fruticose : compo- 

 sition columnar, impalpable ; fracture flat conchoidal, even ; in a 

 second composition it is curved lamellar, the faces of composi- 

 tion being smooth, rough or granulated. Massive : composition 

 granular, impalpable, strongly connected ; fracture, flat conchoi- 

 dal, even. 



Observations. 



The name " Psilomelane" from -^/Xo?, smooth or naked, and p,t- 

 A?, black, is formed in allusion to the black colour and smooth 

 hematitic shapes of this mineral. It is an almost literal transla- 

 tion into Greek, of one of the names applied to this species, in 

 German, " Schwarzer Glaskopf;" the latter, though the ortho- 

 graphy should seem to say the contrary, being surely much more 

 expressive of a " bald head," than of a " vitreous head." 



This is a pretty common species, among those containing 

 manganese. The specimen analyzed is from the neighbourhood 

 of Schneeberg in Saxony, and agrees perfectly with the preced- 

 ing description. It consists of alternating layers, having more or 

 less lustre, disposed in reniform coats. The specific gravity of 

 those portions, which possess a rather stronger lustre, and a con- 

 choidal fracture, is 4.004, while the specific gravity of those 

 without lustre, and an uneven fracture, was found to be 

 = 4.079. 



Psilomelane is one of the most widely diffused ores of man- 

 ganese. It is usually associated with the prismatic manganese- 

 ore, sometimes in a very curious manner. Both of them occur 



